Barton County democrat. [volume] (Great Bend, Kan.) 1885-1915, 1887-08-04
SOUND AND vlBRATIoN.y
Curious Statements of Whose Truth Every
Reader Can Csnxinca HImselE.

Gurious Statements of Whose Truth Every
Reader Can Convince Himself
One person walking over bridge,
stepping slowly, does no injury, be-
cause after each step the bridge recov-
ers before another step is taken; but
when large number of people step in
time to music, we have combined mo-
ton, and the bridge has not time to re-
cover between the steps. Hence, dur
= ing the passage of troops and all we'll
regulated professions over bridge the
music is stopped and the ranks broken.
so that the weight of the crowd is
evenly distributed; while some are put
ting their feet down others are lifting
theirs up. Sometimes fearful accidents
have followed when this breaking of
step has not been observed Once in
France very long bridge went down
under body of soldiers marching over
IN ranks, resulting in the death of
nearly hundred persons. There is far
less danger when bridge is crowded
with people OF cattle, or even many
heavily-laden cars, than when a few
persons are walking over keeping step.
The combination of force is SO great
and vibrations would increase to that
extent that small dog could ruin the
finest and largest bridge if he could
frot back and forth, continually keep
ing exact time.
If we stand near piano and produce
q musical tone with the voice, it will be
a noticed that one particular string will
select that sound and respond to it.
Open the mouth wider, or make the
sound deeper in the chest or at higher
pitch, and the first string will cease,
while another string in the same key as
the voice will take up the strain. If
a hundred tuning-forks of different
tones are sounding at the foot of
an organ pipe, it will choose the one
in accord with it, and respond in that
key alone. The sound called the song
of the sea, so often heard when shells
are placed close to the ear, is merely
the vibrations of the air within the
shell, and two shells placed with their
bells near the ear will increase the roar
If the vibration of the air within is in
unison or sympathy. The same increase
may be seen with two tuning forks;
but if the vibrations are different the
one will counterfeit the other, like the
procession marching out of step, and
no sound will be heard perfectly. Other
substances than air will convey the
sound waves; faint scratch on one
end of long log may be distinctly
heard at the other end, or a stroke on
the end of a long piece of tightly
stretched metal-a bit of copper wire
will communicate the shock to the
other end many hundred feet away.
When bell rings, the tongue strik
ing the side of the bell starts a sound
wave that swells gradually until the
ear is reached, just as the little wave
which stone has disturbed increases
in size until it reaches the shore. If,
when the tongue strikes, the bell is
touching any other substance, a dis
~cordant wave is started which will de-
stroy the one before it, cutting it up, as
it were, as the small wave started at
another point from where we first threw
the stone will meet and .'chop" the
other, and a calm ensues. A contin-
uous blast of air produces no sound,
any more than Il stationary stake in
still water will produce waves, but let
the pillows of air or water strike an OBJ
struction, and sound or waves are seen.
-Harper's Young People.